Many optical devices have been developed to act upon light rays to achieve a variety of desired results. Such inventions have frequently employed reflective and/or prismatic components to produce virtual images of real objects or to create a color spectrum through dispersive effects. In the operation of such prior art devices, planned optical interference of light rays to produce specific interference patterns has not played a role. It will become evident therefore, that the present invention is novel since it discloses an assembly and method for producing certain perceptible light ray interference patterns utilizing a transparent birefractive object.
The scientific phenomenon of perceptible light ray interference most typically occurs when convergent polarized light rays which have substantially the same frequency, but which are out-of-phase, are overlapped on a common optical path. In such instances, the light rays "destructively" interfere at some points to create dark bands, and "constructively" interfere at other points to create bright bands. The configuration of the dark and bright bands will depend upon the phase relationship between the interfering light rays. If the light that is utilized to create an interference is comprised of a plurality of light ray members of the visible light spectrum, (e.g. white light), the resultant interference pattern will be vividly colored.
When visually perceptible light ray interference is induced by passing light rays through a transparent, birefractive object, the phase relationship between the interfering light rays is dictated by the disparate lengths of the different optical paths that are followed by the interfering light rays before they are united on a common optical interference path. The optical path followed by a light ray traveling within a transparent, birefractive object is principally influenced by the orientation of the optical axes within the object, and the refractive index of the object. The orientation of the optical axes is dependent upon the crystalline structure of the object and/or internal stresses within the object, and the type of material comprising the object.